Carbon dots decorated NiCo hydroxycarbonate hierarchical nanoarrays on carbon cloth with high areal capacitance as pseudocapacitor electrode

The electrode materials with low specific capacitance seriously restricts the development of supercapacitors. Herein, CDs modified NiCo hydroxycarbonate (NiCoHC/CDs) hierarchical nanoarrays were grown on carbon cloth (CC) through a simple step by step hydrothermal method. The morphology, crystalline structure and electrochemical performance of the as-prepared NiCoHC nanoarrays on CC can be readily manipulated by varying the concentration of CDs in reaction solution. The optimized NiCoHC/CDs-2 nanoarrays on CC showed a high areal specific capacitance of 14.83 F cm‐2 (1964.64 F g‐1) at a current density of 5 mA cm‐2, excellent rate performance with a high capacitance retention of 46.8% at 50 mA cm‐2 and a good cycle stability with capacitance retention of 76.1% after 3000 cycles at 20 mA cm‐2. Furthermore, an asymmetric aqueous supercapacitor, which assembled using NiCoHC/CDs-2 as cathode and oxidized carbon cloth as anode in 6 M KOH, delivered a specific capacitance of 2.23 F cm‐2 (18.58 F cm‐3) in a potential window of 0‐1.5 V. An energy density of 5.82 mWh cm‐3 can be obtained at the power density of 33.58 mW cm‐3 and maintained 1.90 mWh cm‐3 at 98.99 mW cm‐3. Moreover, after 2000 cycles at 20 mA cm‐2, the device still retained 69.8% capacitance retention.